BMW: BMW error code, bmw 540i, glenn vargas

Question
Thanks for your reply.
The previous owner left the invoice for the replacement of both cat. converters, but they are not BMW equipment.
What do you mean by inspect O2 sensor?  At this point all I know about them is there are 4 of them, one before and one after each of the two cats.  The milage is good, between 24 and 27 mpg on trips.  No check engine lights, and I have not had to go through emission check yet.
I have read that O2 sensors only last about 100K miles.  If this is true for me, is there a way to check if they are the problem?
Any suggestions are greatly appreciated.

Glenn


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Followup To
Question -
Hi,
I recently bought a 97 BMW 540i with six-speed. It has about 110K miles.
I have a code reader and it indicates 'catalytic efficiency cyls 5-8'. The car runs good execpt for some stumbling or surging for the first minute or two while warming up.
The previous owner replaced the cat. converters at about 95K miles.
Is this something that I should be concerned about? What should I check/replace to eliminate?

Thanks,
Glenn Vargas
Answer -
inspect the o2 sensor in the cat. How sure are you that the previous owner did replace the cat? The only problems that this would cause is, check engine light, failed emmissions, and poor gas milage. Between the cat and the sensors in the cat. you probobably have a failure.

hope this helps


Answer
If no check engine light is comming on, no poor gas milage, and your call has a good steady idle; i would leave it alone.  Im not sure what code reader u are  using, but it might be reading wrong as well. Also the aftermarket cat's should not cause anyproblems and a bad O2 sensor will definately throw up a check engine light.

Hope that helps.